Tibia Bivarica

”Shell small, thin-walled, consisting of probably up to 10 whorls. Protoconch small, smooth, rounded; followed by two convex, smooth post-embryonic whorls; later whorls moderately convex, sculptured by several axial ribs and two prominent varices. First sculptured whorl bears almost twice as many fine, greatly curved axial ridges as later whorls. These axial ridges extend almost as far as the suture. The two varices are located almost 180º apart, they are discontinuous from whorl to whorl and are prominently displaced in some adjacent whorls, their ends abut against the suture. Between 10-16 axial ribs are present between the varices on adult whorls. Whorl surface further sculptured by about 13 faint, flat-topped spiral ribs separated by narrow, linear grooves. Suture deeply incised. Base ornamented by about 10 spiral ribs similar to those on body whorl. Columella elongate, straight, and cylindrical. Outer lip margin not preserved. Aperture hemispherical.”